Apparatus for the measurement of tensile stresses on bands,filaments or the like

ABSTRACT

D R A W I N G TESTING APPARATUS FOR MEASUREMENT OF TENSILE STTESSES ON ELONGATED FLEXIBLE BAND-LIKE OR FILAMENTARY PRODUCTS HAS TWO STATIONARY GUIDE ROLLERS AND A MOVABLE TESTING ROLLER WHICH IS DISPLACED THROUGH SHART DISTANCES IN RESPONSE TO CHANGES IN TENSILE STRESSES UPON THE PRODUCT. THE PRODUCT IS TRAINED OVER THE ROLLERS WHEREBY THE TESTING ROLLER CAUSES A TRANSDUCER TO PRODUCE APPROPRIATE SIGNALS WHENEVER THE TESTING ROLLER CHANGES ITS POSITION IN RESPONSE TO A CHANGE IN TENSILE STRESS. THE OPERATING RANGE OF THE TESTING APPARATUS CAN BE BROADENED BY MOVING THE TESTING ROLLER SIDEWAYS INDEPENDENTLY OF THE CHANGES IN TENSILE STRESS TO HEREBY CHANGE THE EXTENT OF OVERLAP BETWEEN THE PRODUCT AND THE PERIPHERIAL SURFACE OF THE TESTING ROLLER.

Mam]! 1973 H. GRUNBAUM 3,720,10

APPARATUS FOR THE MEASUREMENT OF TENSILU STRESSES ON BANDS, FILAMENTS ORTHE LIKE Filed Sept. 5. 1970 United States Patent 3,720,100 APPARATUSFOR THE MEASUREMENT Oi? TENSILE STRESSES ON BANDS, FILAMENTS OR THE LIKEHeinrich Grunbaum, Binningen, Switzerland, assignor to Dr. C.Schachenmann & Co., Basel, Switzerland Filed Sept. 3, 1970, Ser. No.69,270 Claims priority, application Switzerland, Sept. 9, 1969, 13,854/69 Int. Cl. Gilli /04 US. Cl. 73-144 Claims ABSTRACT OF THE DISCLOSURETesting apparatus for measurement of tensile stresses on elongatedflexible band-like or filamentary products has two stationary guiderollers and a movable testing roller which is displaced through shortdistances in response to changes in tensile stresses upon the product.The product is trained over the rollers whereby the testing rollercauses a transducer to produce appropriate signals whenever the testingroller changes its position in response to a change in tensile stress.The operating range of the testing apparatus can be broadened by movingthe testing roller sidewa ys independently of the changes in tensilestress to whereby change the extent of overlap between the product andthe peripheral surface of the testing roller.

BACKGROUND OF THE INVENTION The present invention relates to testingapparatus which are utilized to measure tensile stresses acting onflexible products such as strips, bands, cords, ropes, filaments or thelike. More particularly, the invention relates to improvements intesting apparatus of the type wherein the product to be tested istrained over and exerts a pressure against a movable testing memberwhich in turn influences a signal generator so that the latter producessignals which are indicative of the tensile stress.

A drawback of many presently known testing apparatus is that they cannotmeasure tensile stresses within a sufficiently wide range. Thus, if anapparatus if satisfactory for the measurement of stresses which rangebetween 10-20 kp., it cannot be used to measure stresses between 50-125kp. Certain measuring apparatus are already provided with adjustingmeans to vary the range of their measurements. This is normally achievedby a rather complicated adjustment of the linkage between the testingmember and the signal generator. Such adjustment necessitatesdisconnection of the signal generator from the testing member, anadjustment of the linkage between the two, and a renewed attachment ofthe signal generator. The extent to which the product to be testedengages with the testing member remains unchanged. Such procedureconsumes much time and hence a lengthy interruption in the operation ofthe machine which produces or processes the products. Another drawbackof conventional testing apparatus is that the adjustment to change orbroaden the range of their measurements must be carried out'by skilledpersonnel.

SUMMARY OF THE INVENTION An object of the invention is to provide anovel and improved testing apparatus which is used for determinaice tionof tensile stresses acting on flat, round or otherwise configuratedelongated flexible products and which can be rapidly, accurately andrepeatedly adjusted to select an appropriate range of measurements.

Another object of the invention is to provide a testing apparatus whichis used for determination of tensile stresses acting on products whichmove lengthwise and whose range can be adjusted without necessitatingany interruptions in the transport of products.

A further object of the invention is to provide a single, compact andrugged apparatus which can determine and indicate the magnitude oftensile stresses within a wide range and which can be manipulated bysemiskilled persons.

An additional object of the invention is to provide a novel mounting forthe testing member of the improved testing apparatus.

The invention is embodied in a testing apparatus for the determinationof tensile stresses acting on elongated flexible band-like orfilamentary products. The apparatus comprises a pair of first guidemembers, a movable guide member having a circular peripheral outlinewhereby the product to be tested is trained over the guide members sothat it overlies a portion of each guide member and exerts on themovable guide member a force which is proportional to the tensile stressand to the length of that portion of the product which overlaps themovable guide member, and displacing means for moving the movable guidemember sideways with reference to the first guide members between aplurality of positions in each of which the periphery of the movableguide member is engaged by a product portion of different length. Suchadjustment of the movable guide member serves to change the operatingrange of the testing apparatus.

The movable guide member is movable by a carrier which forms part of thedisplacing means, and the movable guide member is further movable withreference to the carrier through small distances in response to changesin the tensile stress upon the product. Such minimal displacements ofthe movable guide member with reference to the carrier are detected by asuitable transducer (e.g., a differential transformer) which producessignals for transmission to a voltmeter or another suitable gauge topermit visual observation or recordal of measured tensile stresses.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved testing apparatus itself, however, both as to its constructionand its mode of operation, together with additional features andadvantages thereof, will be best understood upon perusal of thefollowing detailed description of certain specific ernbodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic partly sideelevational and partly sectional view of a first testing apparatuswherein the carrier for the testing member is held in a first position;

FIG. 2 illustrates the structure of FIG. 1 but with the testing memberin a second position;

FIG. 3 is a schematic partly side elevational and partly sectional viewof a second apparatus, with the carrier for the testing member in afirst position; and

FIG. 4 illustrates the structure of FIG. 3 but with the carrier in asecond position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 illustrate atesting apparatus which is used to determine tensile stresses acting ona flexible product 4 which may constitute a band, strip, filament, cord,rope or the like. The apparatus comprises a pair of stationary guidemembers 2, 3 here shown as rollers which thank a movable guide member ortesting member 1 mounted for rotation about the axis of a shaft which ismounted in a bearing member or bracket 1b. The product 4 is trained overthe rollers 1-3 so that it overlaps or overlies a portion of theperipheral surface of each roller. The angle u indicates the extent ofoverlap (i.e., the length of contact) between the product 4 and theperipheral surface of the testing roller 1. The bracket 1b exerts apressure against a signal generator 5 which produces signals indicatingthe magnitude of tensile stress on the travelling product 4. The signalgenerator 5 is mounted on the platform 7a of a reciprocable carrier orrod 7 which is guided in a stationary bearing sleeve 6 and forms part ofa displacing mechanism for the testing member 1. This displacingmechanism further includes a two-armed lever 8 which is fulcrumed at 9and can maintain the rod 7 in several predetermined axial positionsincluding those shown in FIGS. 1 and 2. The magnitude of the angle u,and hence the operating range of the testing apparatus, varies inresponse to axial displacement of the rod 7. The displacing meansfurther comprises stops or abutments 8a, 8b which hold the rod 7 againstany downward axial movement in the respective position. Thus, when thestop 8a engages the rod 7 and/ or the lever 8 in the position shown inFIG. 1, the platform 7a cannot move away from the path for the product 4so that changes in the pressure applied by the portion 4a of the product4 upon the peripheral surface of the testing roller 1 will affect thegeneration of appropriate signals which are transmitted to a suitablegauge 5a for visual indication of recorded of the measured tensilestress.

The exact construction of the signal generator 5 and gauge 511 forms nopart of the present invention. For example, the signal generator may bean electrical differential transformer which can produce readilydetectable output signals in response to displacement of the bearingmember 1b with reference to the platform 7 through distances as small as0.2-0.5 mm. or even less. The transformer can be coupled to an elasticelement whose characteristic insures a linear relationship between thevalue of the emitted electrical signal and the applied mechanical force.Thus, such a transformer can be said to constitute a transducer whichcan convert the applied force into an infinite number of proportionalelectrical signals within any practical range of forces supplied by thetesting roller 1.

The testing apparatus of the present invention can utilize with equaladvantage several other types of signal generators, for example acapacitative or photoelectric transducer or a pressure-responsivetransistor. Still further, the apparatus can utilize signal generatorsin the form of hydraulic pressure gauges or the like.

The lever 8 can be pivoted by hand or by remote control to move the rod7 between the positions shown in FIGS. 1 and 2 and, if necessary, to oneor more additional axial positions. Each such position corresponds to adifferent angle u. The tensional stress on the product 4 is shown at Zand the pressure acting on the signal generator 5 are indicated at F.The relationship between the tensional stress and the pressure upon thesignal generator can be expressed by the equation F=2Z sing Thus, if theproduct 4 is in mere print contact with the testing roller 1 (i.e., when11:0), the pressure F also equals Zero. The pressure F reaches a maximumvalue when u equals degrees (F=2Z).

The present invention was made after the discovery that, in actual useof a testing apparatus, there arise situations when the tensile stressesvary within a range which exceeds the capabilities of the signalgenerator in a conventional testing apparatus. If the range of a signalgenerator is 1:5, it being assumed that the accuracy of the signalgenerator remains within an acceptable tolerance range, such a signalgenerator should be capable of being used in testing apparatus whichmeasure tensile stresses of 5-100 kp., i.e., within a range of 1:20. Forexample, the signal generator may be of the type which produces signalswith requisite accuracy when the force F varies between 5-10 lrp. Whenthe force F equals for example 15 kp., the signal generator produces asignal which indicates a force of 10 kp. The object of the presentinvention is to provide a testing apparatus wherein such a signalgenerator can be used to accurately indicate tensile stresses whichproduce forces for exceeding the maximum force that can be accuratelyindicated by the employed signal generator.

It was found that, in certain instances, the range of the improvedtesting apparatus can be broadened sufiiciently if the rod 7 is movablebetween two axial positions, for example, between a first position wherethe angle u equals 11.5 degrees and a second position in which the angleu is 60 degrees. In the first position, F=0.2Z, and in the secondposition, F=Z. In the first position, the apparatus can measure tensilestresses between 25-125 kp., and in the second position tensile stressesbetween 5-25 kp. Thus, the testing apparatus can measure tensilestresses of a minimum magnitude (5 kp.) and a maximum magnitude whichequals 25 times the minimum magnitude. At the same time, the signalgenerator merely covers the permissible range of 1:5.

On the other hand, it is often desirable to effect an adjustment in theposition of the rod 7 and signal generator 5 between positions which areselected in such a way that the respective operating ranges overlap eachother. For example, the rod 7 can be moved between three positions inwhich the apparatus respectively measures stresses of 20-100, 10-50 and5-25 kp. Thus, each next-following position halves the value of tensilestresses in the preceding position. This can be achieved by selectingthe angles u for the three positions of the rod 7 in such a way that thevalue of sin u 2 for each next-following position is twice the value of2 sin 2 for the preceding position. Though the manner of selecting thevarious positions is basically immaterial, it is of substantialpractical advantage to select the positions in such a way that thevalues of for successive positions from a divergent geometricprogression a, ar, ar wherein r is a whole number. This is due to thefact that the gauge 5a need not be provided with several sets of dials,i.e., with a separate dial for each position of the rod 7. The gauge 5amay be a voltmeter whose dial carries graduations indicating tensilestresses in the range of 10-50 kp. The graduations are directlyindicative of the measured tensile stresses in the second position ofthe rod 7. When the rod is moved to the first position (range of 20-100kp.), the value indicated by the graduation which is pinpointed by theneedle of the voltmeter a must be multiplied by two. The value of thepinpointed graduation must be divided by two when the rod 7 is moved tothe third position (range of 5-25 kp.).

As mentioned above, conventional testing apparatus can be adjusted tochange the range of measurements by disconnecting the gauge from thelinkage which connects it to the signal generator, by thereupon changingthe transmission ratio of the linkage, and by reattaching the gauge tosuch linkage. This necessitates lengthy interruptions in the operationof the machine which produces and/or processes the flexible product. Inthe testing apparatus of the present invention, the operation of themachine need not be interrupted at all because the angular position ofthe lever 8 can be changed while the product 4 continues to runlengthwise.

FIGS. 3 and 4 illustrate a second testing apparatus which differs fromthe apparatus of FIGS. 1 and 2 in that the movable guide member ortesting roller 1 is located at one side of the path for the product 4and that the stationary guide rollers 2, 3 are located at the other sideof the path. Such mounting of the rollers 1-3 can present problems inconnection with initial treading of the product 4 through the testingapparatus. Therefore, the lever 8 is preferably mounted in such a waythat it can move the rod 7 to at least two positions (such as thoseshown in FIGS. 3 and 4) and a further or retracted position in which thetesting roller 1 is moved upwardly and away from a common tangent forthe guide rollers 2, 3 so that the leading end of the product 4 can bereadily introduced by hand. For example, when the lever 8 assumes theangular position of FIG. 3, it can be moved sideways (as indicated bythe arrow 50) to move the roller 1 upwardly and beyond the position ofFIG. 3 so that the threading of the product can be readily performed byhand. The retracted position of the testing roller 1 is preferably suchthat the workman can thread the product by advancing it along a straightpath between the uppermost points of the guide rollers 2, 3 and thelowermost point of the testing roller 1. It is clear that the apparatusof FIGS. l-Z or 3-4 can be used in inverted position so that all of therollers are located below the path of the product 4 (inversion of theapparatus shown in FIGS. 1-2) or that the axis of the testing roller islocated below the axes of the guide rollers 2, 3 (inversion of theapparatus shown in FIGS. 3-4). Furthermore, the axes of the rollers 1-3need not be located in horizontal planes. It is further clear that therod 7 can be replaced with an eccentric, a lever or another carrierwhich is movable along an arcuate path rather than along a straightpath, as long as the rod or an analogous carrier can move the testingroller in directions at right angles to its axis and transversely of thepath for the product 4. It is also clear that the testing apparatus neednot employ a single testing roller and that the testing roller need notbe flanked by the other two rollers. For example, the roller 2 or 3 canbe moved by the rod 7 or an analogous carrier while the roller 3 or 2and the roller 1 rotate about fixed axes. Finally, the signal generator5 need not share the movements of the carrier for the testing roller, aslong as the intensity or another characteristic of its signals variesproportionally with changes in the angle w.

Certain presently known testing apparatus are already provided with atesting roller which is movable to change the magnitude of the angle ofoverlap between the peripheral surface of such testing roller and thetested product. However, such adjustments in the extent of overlapbetween the product and the testing roller are not utilized to changethe range of measurements of the testing apparatus but rather to producecounteracting or reaction forces whose magnitude is not proportional tothat of tensile stresses. In fact, the magnitude of such reaction forcesoften remains unchanged. On the other hand, the improved testingapparatus, wherein the distances covered by the testing roller 1 inresponse to changes in tensile stresses in the product 4 are extremelysmall, can maintain the ratio between the reaction forces and thetensile stresses at a constant value so that the changes in the angle acan be used exclusively to change the operating range of the testingapparatus.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. In a testing apparatus for the determination of tensile stresses inelongated flexible band-like or filamentary products, a combinationcomprising a first pair of guide members; a movable guide member havinga circular peripheral outline, the product to be tested being trainedover said guide members so that it overlies a portion of each guidemember whereby the product exerts on said movable guide member a forcewhich is proportional to the tensile stress and to the length of theportion of the product which overlaps said movable guide member, saidmovable guide member being movable to an arrestable in a plurality ofpredetermined positions wherein the sine values of the halves of anglesalong which the product overlaps said movable guide member in saidpredetermined positions of said movable guide member form a geometricprogression of whole numbers; signal generating means connected to saidmovable guide member for movement therewith for generating signalsindicating said force without practically changing the relative positionof said movable guide member and said signal generating means; anddisplacing means for moving said movable guide member between at leasttwo of said predetermined positions and for arresting the same in eachof said positions to thereby change the metering range of said testingapparatus.

2. A combination as defined in claim 1, wherein said first guide membersare rollers and said movable guide member is also a roller which ismovable by said displacing means at right angles to its axis.

3. A combination as defined in claim 2, wherein said guide membersdefine for the product a path and wherein such path is flanked by two ofsaid members on one side and by the third member on the other sidethereof, said third guide member constituting said movable guide mem herand being movable by said displacing means to a retracted position inwhich the product can be manually advanced along said path.

4. A combination as defined in claim 2, wherein said bmovable guidemember is flanked by said first guide memers.

5. A combination as defined in claim 1, wherein said displacing meanscomprises a reciprocable carrier for said movable guide member and stopmeans for locating said carrier in each position of said movable guidememher.

6. A combination as defined in claim 1, wherein said displacing meanscomprises a carrier for said movable guide member, said carrier beingturnable about a predetermined axis to move said movable guide memberbetween said positions.

7. A combination as defined in claim 1, and including indicating meansconnected to said signal generating means for visually indicating theforce acting on said movable guide member in correspondence with thesignals produced by said signal indicating means, the measuring range ofsaid indicating means being changed in each of said predeterminedpositions of said movable guide member.

8. A combination as defined in claim 1, wherein said displacing meanscomprises a carrier for said movable guide member, said movable guidemember being displaceable through a minute distance with reference tosaid carrier in response to changes in tensile stress on the product,and further comprising signal generating means for producing in responseto displacement of said movable guide member with reference to saidcarrier signals whose magnitude is indicative of the tensile stress onthe product.

9. A combination as defined in claim 8, wherein said signal generatingmeans is mounted on said carrier.

10. A combination as defined in claim 1, wherein said movable guidemember is movable between such positions that the operating ranges ofsaid apparatus overlap member.

References Cited UNITED STATES PATENTS 3,310,981 3/1967 Nixon et a].73-144 1,987,815 1/1935 Bartol 73-144 2,528,883 11/1950 Hayward 731441,833,195 11/1931 Albright 73--144 1,722,036 7/1929 Byl 73-144 FOREIGNPATENTS 803,811 11/1958 Great Britain 73l44 891,232 3/ 1962 GreatBritain 73--144 RICHARD C. QUEISSER, Primary Examiner H. GOLDSTEIN,Assistant Examiner

